This invention relates to a vortex flow control device.
Vortex flow control devices, or “vortex valves”, are used, for example, in storm water systems to restrict the flow rate of storm water to a main sewer under heavy flow conditions. For example, a gully receiving storm water from kerbside gratings may be provided with a vortex flow control device at its outlet so that, under storm conditions, the outflow from the gully is restricted. If the inflow to the gully exceeds the outflow as controlled by the flow control device, water accumulates in the gully until conditions ease.
Such a device is disclosed in GB 2409537. The device comprises a housing having oppositely disposed end walls and an outer wall which extends about an axis and is disposed between the end walls. One of the end walls has an outlet positioned generally on the axis, and the housing also has an inlet directed tangentially of the axis so that, when the pressure head above the device exceeds a certain value, the inflowing water generates a vortex within the housing so restricting outflow through the outlet.
In the device of GB 2409537, the inlet is constituted by a circumferential gap in the outer wall, the size of which can be varied by means of a sliding arcuate plate. Thus, the same housing can be used to provide a vortex flow control device having different characteristics, achieved by appropriate positioning of the arcuate plate. Also, a vortex flow control device that has already been installed can have its characteristics altered, for example if there is a change in the flow regime in which it operates, by adjusting the arcuate plate.
Another such device, referred to as a vortex throttle, is disclosed in U.S. Pat. No. 5,524,393. The device described is for controlling water run-off from roofs.
According to one aspect of the present invention, there is provided a vortex flow control device comprising a housing defining a vortex chamber, the housing comprising oppositely disposed end walls and an outer wall extending about an axis and disposed between the end walls, the outer wall comprising a curved portion which extends around the axis, one end of the curved portion adjoining a planar portion which extends in a tangential direction with respect to the axis to a first free edge, and the other end of the curved portion adjoining a terminal portion which extends in a direction towards the planar portion and terminates at a second free edge, an outlet from the housing being disposed in one of the end walls, and an inlet to the housing being defined in the outer wall between the second free edge and the planar portion, the inlet being configured so that fluid entering the vortex chamber through the inlet induces a circulating flow within the vortex chamber about the axis, characterised in that the terminal portion is directed away from the circulating flow in the direction towards the upstream edge, whereby turbulence is induced in the region of the inlet by fluid entering the vortex chamber through the inlet, the terminal portion being inclined to the planar portion at an angle not less than 85° and not more than 95°.
In an embodiment of such a device, the outer wall may be fabricated from first and second outer wall components, the first outer wall component comprising the planar portion and the curved portion, and the second outer wall component comprising the terminal portion which is secured to the end walls and to the curved portion.
The terminal portion may be oriented so that it is directed from the curved portion towards the free edge of the planar portion. The inlet may lie in a plane which is perpendicular to the tangential direction of the planar portion.
The curved portion of the outer wall may extend around the axis over an angle of not less than 270°. In a specific embodiment, the planar portion and the terminal portion are substantially perpendicular to each other.
According to another aspect of the present invention, there is provided a method of manufacturing a vortex flow control device comprising a housing defining a vortex chamber, the housing comprising oppositely disposed end walls and an outer wall extending about an axis and disposed between the end walls, an outlet from the housing being disposed in one of the end walls, and an inlet to the housing being disposed in the outer wall and configured so that fluid entering the vortex chamber through the inlet induces a circulating flow within the vortex chamber about the axis, the inlet being defined between an upstream edge and a downstream edge of the outer wall with respect to the direction of the circulating flow in the region of the inlet, the upstream edge being an edge of a terminal portion of the outer wall, characterised in that the method comprises the steps of:                (a) manufacturing a template unit comprising the end walls and a partial outer wall excluding the terminal portion; and        (b) subsequently securing the terminal portion of the outer wall to the template unit.        
The length of the terminal portion, between the second transition and the downstream edge, may be determined on the basis of the required characteristics of the vortex flow control device.
According to a third aspect of the present invention, there is provided a method of manufacturing a vortex flow control device comprising a housing defining a vortex chamber, the housing comprising oppositely disposed end walls and an outer wall extending about an axis and disposed between the end walls, an outlet from the housing being disposed in one of the end walls, and an inlet to the housing being disposed in the outer wall and configured so that fluid entering the vortex chamber through the inlet induces a circulating flow within the vortex chamber about the axis, the inlet being defined between an upstream edge and a downstream edge of the outer wall with respect to the direction of the circulating flow in the region of the inlet, the upstream edge being an edge of a terminal portion of the outer wall, characterised in that the method comprises the steps of:                (a) manufacturing a plurality of identical template units, each comprising the end walls and a partial outer wall excluding the terminal portion;        (b) determining desired characteristics of a vortex flow control device to be supplied;        (c) determining the required dimensions of a terminal portion to be secured to one of the template units to provide the desired characteristics; and        (d) securing a terminal portion of the required dimensions to the said one template unit.        
The second planar portion may be secured to the template unit by welding.
In an alternative embodiment of the vortex flow control device, the housing may comprise a one-piece molding.
According to a fourth aspect of the present invention, there is provided a method of manufacturing a vortex flow control device comprising a housing which is a one-piece molding defining a vortex chamber, the housing comprising oppositely disposed end walls and an outer wall extending about an axis and disposed between the end walls, an outlet from the housing being disposed in one of the end walls, and an inlet to the housing being disposed in the outer wall and configured so that fluid entering the vortex chamber through the inlet induces a circulating flow within the vortex chamber about the axis, the inlet being defined between an upstream edge and a downstream edge of the outer wall with respect to the direction of the circulating flow in the region of the inlet, the upstream edge being an edge of a terminal portion of the outer wall, characterised in that the method comprises the steps of:                (a) manufacturing a template unit comprising the end walls and the outer wall;        (b) removing a region of the outer wall to form the free edges of the terminal portion and the planar portion, thereby forming the inlet with a desired dimension.        
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:—